RE : RE : [lwip-users] "the ARP layer is notprotectedagainstconcurrentaccess"

[Frédéric BERNON]

Ok Simon, just see there what I think to propose. Like for the arp_timer 
initialize, I think it MUST be done like this. I don't think it's change 
something for RAW API users, except they have to set TCPIP_PACKET_INPUT to 0 
(and in fact, because it's driver dependant, it's only change the ethernetif 
skeleton). Kieran, Simon (and others), what's your opinon?

In opt.h

#ifndef TCPIP_PACKET_INPUT
#define TCPIP_PACKET_INPUT 1
#endif

In ethernetif.c :

static void
ethernetif_input(struct netif *netif)
{
  struct ethernetif *ethernetif;
  struct eth_hdr *ethhdr;
  struct pbuf *p;

  ethernetif = netif->state;
  
  /* move received packet into a new pbuf */
  p = low_level_input(netif);
  /* no packet could be read, silently ignore this */
  if (p == NULL) return;
 
  /* points to packet payload, which starts with an Ethernet header */
  ethhdr = p->payload;

#if LINK_STATS
  lwip_stats.link.recv++;
#endif /* LINK_STATS */
   
  switch (htons(ethhdr->type)) {
#if TCPIP_PACKET_INPUT

    /* ARP or IP packet? */
    case ETHTYPE_IP:   
    case ETHTYPE_ARP:
      /* full packet send to tcpip_thread */
      netif->input(p, netif);
      break;

#else

    /* IP packet? */
    case ETHTYPE_IP:
      #if ETHARP_TRUST_IP_MAC
      /* update ARP table */
      etharp_ip_input( netif, p);
      #endif
      /* skip Ethernet header */
      pbuf_header(p, -sizeof(struct eth_hdr));
      /* pass to network layer */
      netif->input(p, netif);
      break;
      
    case ETHTYPE_ARP:
      /* pass p to ARP module  */
      etharp_arp_input(netif, ethernetif->ethaddr, p);
      break;

#endif

    default:
      pbuf_free(p);
      p = NULL;
      break;
  }

}

And in tcpip.c:

#if TCPIP_PACKET_INPUT
err_t packet_input(struct pbuf *p, struct netif *inp)
{
  struct ethernetif *ethernetif;
  struct eth_hdr *ethhdr;
  struct pbuf *p;

  ethernetif = netif->state;
 
  /* points to packet payload, which starts with an Ethernet header */
  ethhdr = p->payload;

#if LINK_STATS
  lwip_stats.link.recv++;
#endif /* LINK_STATS */
    
  switch (htons(ethhdr->type)) {
    /* IP packet? */
    case ETHTYPE_IP:
      #if ETHARP_TRUST_IP_MAC
      /* update ARP table */
      etharp_ip_input( netif, p);
      #endif
      /* skip Ethernet header */
      pbuf_header(p, -sizeof(struct eth_hdr));
      /* pass to IP layer */
      ip_input(p, netif);
      break;
      
    case ETHTYPE_ARP:
      /* pass p to ARP module  */
      etharp_arp_input(netif, ethernetif->ethaddr, p);
      break;

    default: /* Not really necessary, but...*/
      pbuf_free(p);
      p = NULL;
      break;
  }
}
#endif /* TCPIP_PACKET_INPUT */

static void
tcpip_thread(void *arg)
{
  struct tcpip_msg *msg;
  
#if IP_REASSEMBLY
  sys_timeout( 1000, ip_timer, NULL);
#endif
  if (tcpip_init_done != NULL) {
    tcpip_init_done(tcpip_init_done_arg);
  }
  
  while (1) {                          /* MAIN Loop */    
    sys_mbox_fetch(mbox, (void *)&msg, 0);
    switch (msg->type) {
    case TCPIP_MSG_API:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: API message %p\n", (void *)msg));
      api_msg_input(msg->msg.apimsg);
      break;
    case TCPIP_MSG_INPUT:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: IP packet %p\n", (void *)msg));
      #if TCPIP_PACKET_INPUT
      packet_input(msg->msg.inp.p, msg->msg.inp.netif);
      #else
      ip_input(msg->msg.inp.p, msg->msg.inp.netif);
      #endif
      break;
    case TCPIP_MSG_CALLBACK:
      LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: CALLBACK %p\n", (void *)msg));
      msg->msg.cb.f(msg->msg.cb.ctx);
      break;
    default:
      break;
    }
    memp_free(MEMP_TCPIP_MSG, msg);
  }
}

 
  
====================================
Frédéric BERNON 
HYMATOM SA 
Chef de projet informatique 
Microsoft Certified Professional 
Tél. : +33 (0)4-67-87-61-10 
Fax. : +33 (0)4-67-70-85-44 
Email : address@hidden 
Web Site : http://www.hymatom.fr 
====================================
P Avant d'imprimer, penser à l'environnement
 


-----Message d'origine-----
De : address@hidden [mailto:address@hidden De la part de Goldschmidt Simon
Envoyé : lundi 5 mars 2007 11:43
À : Mailing list for lwIP users
Objet : RE: RE : [lwip-users] "the ARP layer is 
notprotectedagainstconcurrentaccess"


Hi Frédéric,

> >The solution which Frédéric proposed is simpler, but sends
> ALL packets to the tcpip_thread. Filtering them before
> passing on seemed more performant to me.
> 
> Yes, I've got the same idea yesterday :) Even if on a
> "classic" network, most of packets are IP & ARP, there is 
> some others packets for STP or other Ethernet level protocols 
> (in my network, there is something like 120 devices, and, in 
> 5 sec, there is something like 15 "low-level" packets).
> 
> This is always the same problem  : more code in "receive"
> thread (so footprint increase), to save processor time. I 
> don't think this this a problem, and I can propose a "clean" 
> patch if Simon is ok with this solution...

Of course I would like to see your patch, although I already have one myself 
(since I'm using the stack this way, already). I think it's always better to 
see another idea, so if you have a patch, please submit it, I'll file a bug 
entry.

Simon


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